A walking dragline typically includes a main housing and a boom that extends upwardly and outwardly from the main housing and has thereon a sheave for supporting a hoist rope. The hoist rope extends from a bucket hoist mechanism and over the sheave to a bucket for causing vertical movement of the bucket. A drag rope extends between a bucket drag mechanism and the bucket for causing horizontal movement of the bucket. The main housing is supported by a tub that sits on the ground when the dragline is engaged in digging operations. Two matching walk mechanisms are mounted on opposite sides of the main housing and are operable for moving the main housing over the ground between digging operations.
U.S. Pat. No. 5,245,882 discloses a walk mechanism of typical construction. A walk mechanism ordinarily includes a shoe for engaging the ground during walking movement. The shoe is fixed to a walk leg housing that is mounted on an eccentric. The eccentric is fixed to a main walk shaft and rotates at about one revolution per minute. The eccentric is connected by a knee link to the main housing through a journal bearing and a pin fixed to the main housing, such that rotation of the eccentric causes the walk leg housing to pivot, thereby causing walking movement of the shoe. The motion of the knee link relative to the pin is oscillatory and pivotal. The journal bearing facilitates the pivoting movement between the knee link and the pin.
U.S. Pat. No. 5,320,431 discloses a walk mechanism journal bearing design typical of prior art constructions. Various grease groove arrangements have been tried to provide effective lubrication within the bearing. Those shown include opposed sine waves, axially-directed grooves, and angled grooves cut into the interior cylindrical surface of the bearing.
For proper function and life, a suitable film of lubricant should always be present between a bearing surface and the mating contact surface in the area of relative motion. To accomplish this, a predetermined amount of lubricant is forced into a groove pattern that carries the lubricant to the desired areas. If the lubrication system fails or does not provide adequate mounts, all surfaces in contact may not have the proper film thickness during operation. The end result could be accelerated wear of both the bearing and the mating surface.
One problem with conventional dragline walk mechanisms is wear on the walk mechanism components, particularly the journal bearing, that is compounded by the relative inaccessibility of the journal bearing. The wear is due in large part to inadequate lubrication in the bearing, and to insufficient bearing surfaces in the highest-loaded regions of the bearing.